Some medical systems incorporate one or more implantable medical devices (IMDs). Some systems include a primary IMD, and one or more secondary IMDs. The secondary IMDs may include, for example, one or more sensors configured to collect data based on measurements taken within a patient's body. For example, secondary IMDs may include sensors that measure blood pressure, temperature, heart rate, blood composition, patient activity, or other indicators of patient health.
Because most implantable sensors are configured to be disposed within one or more structures of a patient, (e.g., the patient's heart, veins, arteries, etc.), the size and shape of such devices is a primary concern. Because of size concerns, secondary IMDs may not include an internal battery. Instead, secondary IMDs may be powered by a battery of the primary IMD. Secondary IMDs may also not include an independent accurate clock source. Thus, it may be desirable to synchronize a secondary IMD clock to a clock of a primary IMD.